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ForwardCharacterIterator Class Reference

Abstract class that defines an API for forward-only iteration on text objects. More...

#include <chariter.h>

Inheritance diagram for ForwardCharacterIterator:

CharacterIterator UCharCharacterIterator StringCharacterIterator

Public Types

enum  { DONE = 0xffff }
 Value returned by most of ForwardCharacterIterator's functions when the iterator has reached the limits of its iteration. More...

Public Member Functions

virtual ~ForwardCharacterIterator ()
 Destructor.
virtual UBool operator== (const ForwardCharacterIterator &that) const =0
 Returns true when both iterators refer to the same character in the same character-storage object.
UBool operator!= (const ForwardCharacterIterator &that) const
 Returns true when the iterators refer to different text-storage objects, or to different characters in the same text-storage object.
virtual int32_t hashCode (void) const =0
 Generates a hash code for this iterator.
virtual UClassID getDynamicClassID (void) const =0
 Returns a UClassID for this ForwardCharacterIterator ("poor man's RTTI").
virtual UChar nextPostInc (void)=0
 Gets the current code unit for returning and advances to the next code unit in the iteration range (toward endIndex()).
virtual UChar32 next32PostInc (void)=0
 Gets the current code point for returning and advances to the next code point in the iteration range (toward endIndex()).
virtual UBool hasNext ()=0
 Returns FALSE if there are no more code units or code points at or after the current position in the iteration range.

Protected Member Functions

 ForwardCharacterIterator (const ForwardCharacterIterator &)
ForwardCharacterIteratoroperator= (const ForwardCharacterIterator &)

Detailed Description

Abstract class that defines an API for forward-only iteration on text objects.

This is a minimal interface for iteration without random access or backwards iteration. It is especially useful for wrapping streams with converters into an object for collation or normalization.

Characters can be accessed in two ways: as code units or as code points. Unicode code points are 21-bit integers and are the scalar values of Unicode characters. ICU uses the type UChar32 for them. Unicode code units are the storage units of a given Unicode/UCS Transformation Format (a character encoding scheme). With UTF-16, all code points can be represented with either one or two code units ("surrogates"). String storage is typically based on code units, while properties of characters are typically determined using code point values. Some processes may be designed to work with sequences of code units, or it may be known that all characters that are important to an algorithm can be represented with single code units. Other processes will need to use the code point access functions.

ForwardCharacterIterator provides nextPostInc() to access a code unit and advance an internal position into the text object, similar to a return text[position++].
It provides next32PostInc() to access a code point and advance an internal position.

next32PostInc() assumes that the current position is that of the beginning of a code point, i.e., of its first code unit. After next32PostInc(), this will be true again. In general, access to code units and code points in the same iteration loop should not be mixed. In UTF-16, if the current position is on a second code unit (Low Surrogate), then only that code unit is returned even by next32PostInc().

For iteration with either function, there are two ways to check for the end of the iteration. When there are no more characters in the text object:

Example:

 void function1(ForwardCharacterIterator &it) {
     UChar32 c;
     while(it.hasNext()) {
         c=it.next32PostInc();
         // use c
     }
 }

 void function1(ForwardCharacterIterator &it) {
     UChar c;
     while((c=it.nextPostInc())!=ForwardCharacterIterator::DONE) {
         // use c
      }
  }


Member Enumeration Documentation

anonymous enum
 

Value returned by most of ForwardCharacterIterator's functions when the iterator has reached the limits of its iteration.


Constructor & Destructor Documentation

virtual ForwardCharacterIterator::~ForwardCharacterIterator  )  [inline, virtual]
 

Destructor.


Member Function Documentation

virtual UClassID ForwardCharacterIterator::getDynamicClassID void   )  const [pure virtual]
 

Returns a UClassID for this ForwardCharacterIterator ("poor man's RTTI").

Despite the fact that this function is public, DO NOT CONSIDER IT PART OF CHARACTERITERATOR'S API!

Implemented in StringCharacterIterator, and UCharCharacterIterator.

virtual int32_t ForwardCharacterIterator::hashCode void   )  const [pure virtual]
 

Generates a hash code for this iterator.

Implemented in UCharCharacterIterator.

virtual UBool ForwardCharacterIterator::hasNext  )  [pure virtual]
 

Returns FALSE if there are no more code units or code points at or after the current position in the iteration range.

This is used with nextPostInc() or next32PostInc() in forward iteration.

Implemented in UCharCharacterIterator.

virtual UChar32 ForwardCharacterIterator::next32PostInc void   )  [pure virtual]
 

Gets the current code point for returning and advances to the next code point in the iteration range (toward endIndex()).

If there are no more code points to return, returns DONE.

Implemented in UCharCharacterIterator.

virtual UChar ForwardCharacterIterator::nextPostInc void   )  [pure virtual]
 

Gets the current code unit for returning and advances to the next code unit in the iteration range (toward endIndex()).

If there are no more code units to return, returns DONE.

Implemented in UCharCharacterIterator.

UBool ForwardCharacterIterator::operator!= const ForwardCharacterIterator that  )  const [inline]
 

Returns true when the iterators refer to different text-storage objects, or to different characters in the same text-storage object.

virtual UBool ForwardCharacterIterator::operator== const ForwardCharacterIterator that  )  const [pure virtual]
 

Returns true when both iterators refer to the same character in the same character-storage object.

Implemented in StringCharacterIterator, and UCharCharacterIterator.


The documentation for this class was generated from the following file:
Generated on Sun May 22 18:53:58 2005 for ICU 2.1 by  doxygen 1.4.2